Heart failure is defined as a condition in which a person's heart is no longer capable of supplying adequate blood flow to meet the needs of the body. Congestive heart failure (CHF) refers to a condition wherein the heart does not transfer blood to end organs efficiently or it has to do so with increased filling pressures. CHF, rather than being its own disease, occurs as a result of any one, or combination, of a number of conditions which affect the heart, including, but not limited to, myocardial infarction, dilated cardiomyopathy, valvular heart disease, hypertension, obesity, diabetes, and cigarette smoking. All of these conditions can lead to CHF by overloading or causing damage to the heart muscle.
It has been estimated that nearly 5 million Americans have CHF. Increasing prevalence, hospitalizations, and deaths have made CHF a major chronic condition in the United States and throughout the world. After the diagnosis of CHF, the death rate is 50% within 5 years. Each year, there are more than 400,000 new cases in the United States alone. The prevalence of CHF is increasing as the population ages.
Therapies for patients suffering from CHF include medical, surgical, and biopharmaceutical (for example, growth factors, cytokines, myoblasts, and stem cells). Improvement in prognosis through medical therapy has reached a ceiling. There is widespread thought that current medical therapies cannot be effectively expanded upon. Heart transplant is an effective surgical remedy for patients with CHF. However, the demand far outstrips the availability of donor hearts. Therefore, a mechanical solution is sorely needed to treat heart failure.
Typically for mechanical treatment of CHF, a pump such as a ventricular assist device (VAD) is implanted in a patient awaiting a heart transplant. The VAD is implanted as a “bridge to transplant” or “destination therapy” for those weakened hearts that are expected to become unable to pump enough blood to sustain life. A VAD is typically attached to the left ventricle and draws blood from the left ventricle and sends the blood to the aorta.
A number of other devices have been proposed for assisting the diseased heart and supporting decompensated hemodynamics. For example, U.S. Pat. No. 5,911,685, assigned to Impella Cardiosystems AG, describes “An intravascular microaxial flow pump, comprising: a cylindrical drive unit of preselected outer diameter having an electric motor disposed therein driving a shaft distally extending therefrom wherein such shaft is supported solely by two bearings, one located at the extreme proximal end of said drive unit and another at the extreme distal end of said drive unit; a cylindrical intravascular microaxial flow pump housing rigidly attached to said drive unit having essentially the same preselected outer diameter and oriented to be coaxially and distally disposed with respect to said drive unit; and an impeller disposed within said pump housing, rigidly affixed to said shaft, and located immediately adjacent said distal bearing, operative to draw fluid into and through said housing and over said drive unit.”
In addition, U.S. Pat. No. 7,125,376, assigned to Thoratec Corporation, describes “An intravascular extracardiac pumping system for supplementing blood circulation through a patient experiencing congestive heart failure without any component thereof being connected to the patient's heart, the extracardiac system comprising: a pump configured to pump blood through the patient at subcardiac volumetric rates, said pump having an average flow rate that, during normal operation thereof, is substantially below that of the patient's heart when healthy, the pump configured to be positioned within the vasculature of a patient; an inflow conduit fluidly coupled to the pump to direct blood to the pump, the inflow conduit configured to be positioned within the vasculature of the patient; and an outflow conduit fluidly coupled to the pump to direct blood away from the pump, the outflow conduit configured to be positioned within the vasculature of the patient; whereby the pump and the inflow and outflow conduits are configured so as to be inserted subcutaneously into the vasculature in an minimally-invasive procedure; and wherein the pump comprises an impeller.”
A cardiac recovery is possible for patients who suffer from CHF, especially through treatment with biopharmaceuticals. The likelihood of cardiac recovery is believed to be increased by reducing the stress on the heart from the decompensated state. However, the existence of a VAD surgically inserted into the heart reduces the likelihood of cardiac recovery from CHF. The gold standard for treatment of advanced heart failure is a heart transplant but the scarcity of transplantable hearts makes this impossible for the vast majority of patients.
Therefore, there exists a need for a hemodynamic assist device that can be implanted and retrieved in a minimally invasive manner, without damaging the heart and preventing cardiac recovery.